We are studying the pathogenesis, epidemiology, and economic impact of postoperative infections. We have designed a quantitative method for sampling low levels of bacterial contaminations of wound surfaces using a micropore filter mounted on a nutritive agar media. We are evaluating the clinical application of this technique in an animal model prior to human use. Our clinical studies have delineated risk factors which predispose to the development of postoperative pneumonias and have identified possible ways to reduce the likelihood of their occurrence. We have shown that some practices (i.e., bacterial anesthesia filters) which were introduced to prevent pneumonias are ineffective and add great cost to our health care budget unnecessarily. We have studied patterns of use and abuse of prophylactic antibiotics in surgery in 21 Utah hospitals. We found that prophylaxis was often prescribed too early, too late or too long and that prophylaxis was not indicated on approximately 80% of the days on which it was prescribed. Other clinical studies are attempting to define the infectious consequences of misused prophylactic antibiotics as well as the direct costs associated with specific postoperative infections.